The present invention relates to a control for an automatic transmission, and more particularly to an adaptive self-adjustment of an automatic transmission to change an amount of input torque owing to operation of an engine driven auxiliary device.
Japanese Patent Application First (unexamined) Publication No. 58-34258 discloses a control for an automatic transmission wherein a gear shift is controlled in response to the output signals of a throttle opening degree sensor and a vehicle speed sensor and a line pressure used for actuating hydraulically actuable frictionally engageable couplings is varied in the same pattern as actual engine torque varies. For this line pressure control, a throttle valve which is operatively coupled via a cam with the engine throttle valve is provided. Specifically, with the same throttle opening, the same amount of line pressure is produced.
According to this known line pressure control, the amount of line pressure becomes higher than necessary for the actually supplied torque to the automatic transmission when an auxiliary device is in operation to consume the engine power output and reduce the amount of actually supplied torque to the automatic transmission.
An object of the present invention is to provide a control for an adaptive self-adjustment of an automatic transmission to a change in actual input torque in response to an operation of an auxiliary device.